Various sensors are known in the magnetic-effect sensing arts. Examples of common magnetic-effect sensors include, for example, magnetoresistive and Hall effect technologies. Such magnetic sensors can generally respond to a change in the magnetic field as influenced by the presence or absence of a ferromagnetic target object of a designed shape passing by the sensory field of the magnetic-effect sensor. The sensor can then provide an electrical output, which can be further modified as necessary by subsequent electronics to yield sensing and control information. The subsequent electronics may be located either onboard or outboard of the sensor package.
Many automotive electronic systems utilize position sensors for a number of related applications. Such position sensors typically incorporate magnetic sensors, including for example, ring magnets. Ring magnets are well known in the magnetic sensing arts and when employed in the context of automotive sensors, typically span transmission, crankshaft, and camshaft applications. When position sensors for automotive electronic systems were originally conceived and developed, such sensors were primarily utilized for the determination of clutch pedal and shift lever positions in automobile transmission applications. Reasonably accurate linear position sensing is required to identify the positions of the clutch pedal and the shift lever, using electrical signals from a non-contacting sensor approach.
In automated manual transmission applications, for example, two sensors may be required to sense the shift lever position as it moves in an H-pattern from Reverse to Low to Second to Third gear. For a standard automatic transmission application, where the shift lever moves along a single axis direction, one position sensor may be required to sense whether the shift lever is in one of the Drive-Mode operating positions (i.e., Forward, Reverse, Neutral, Over-Drive, Low, etc.) as well as any positions between such operating conditions.
Many of the sensors utilized in automotive applications employ a 60-2 digital tooth pulse train from their crankshaft sensor. A typical 60-2 digital tooth pulse train is generated from 60 equally spaced teeth with 2 teeth thereof removed for a reference. This type of configuration can be obtained by providing either a 58 tooth metal target, or a 58 pole pair ring magnet incorporated thereof. The automotive industry is currently focusing on 60-2 pulse patterns for its crankshaft application. This is, of course, subject to change depending upon the shifting needs of the industry.
One of the problems that such conventional configurations produces is a resulting output that is dependent upon target rotation, thereby requiring a larger number of poles at the associated ring magnet. Conventional configurations require a large number of poles to produce a particular pulse pattern because they generally produce one pulse per pole pair, which in essence means that such devices are sensitive to magnet polarities. Because a larger number of poles are required, the magnet pole widths are very narrow. These narrow pole widths prevent greater magnetic influence at the magnetic sensor, resulting in sometimes faulty or inefficient readings, which in turn can cause failure in automotive applications.
The present inventors have thus concluded that a need exists for improved magnetic sensor methods and systems, which utilize ring magnets. In particular, the present inventors believe that these problems can be overcome through the application of the invention described herein.